Image Projection Apparatus, Method of Controlling Image Projection Apparatus, and Storage Medium

1. An image projection apparatus comprising: a light source to emit light; a light modulator to modulate intensity of the light emitted from the light source for generating a projection image; and an image luminance controller to control the light modulator to maintain brightness of the projection image projected on a projection face at a substantially constant level during a given time period of the image projection apparatus, the given time period being from one time point when power supply to the image projection apparatus is started to another time point when a power level for driving the light source is increased to a given power level.

2. The image projection apparatus of claim 1 , further comprising: an image capturing unit to capture a pattern image used for an auto focusing control operation projected on the projection face; and a focus controller to perform an auto focusing control operation based on the pattern image captured by the image capturing unit during the given time period while the brightness of the projected pattern image is being maintained at the substantially constant level.

3. The image projection apparatus of claim 1 , wherein the image luminance controller controls the light modulator to decrease a gradation value of one or more pixels included in original image data so that the brightness of the projection image is maintained at the substantially constant level during the given time period.

4. The image projection apparatus of claim 3 , wherein the light modulator is a digital micro-mirror device (DMD), wherein the image luminance controller gradually decreases a duty ratio of the light modulator when a power level for driving the light source is being increased during the given time period, and returns the decreased duty ratio to a given duty ratio when the given time period ends.

5. The image projection apparatus of claim 1 , wherein the image luminance controller controls an aperture level of an optical system of the image projection apparatus so that the brightness of the projection image is maintained at the substantially constant level during the given time period.

6. The image projection apparatus of claim 2 , wherein the image luminance controller completes a control of maintaining the brightness of the projection image at the substantially constant level when the auto focusing control operation is completed.

7. The image projection apparatus of claim 1 , wherein the image luminance controller completes a control of maintaining the brightness of projection image at the substantially constant level when the power level for driving the light source is increased to the given power level.

8. The image projection apparatus of claim 1 , wherein the image luminance controller controls the light modulator to increase the brightness of the projection image gradually when the power level for driving the light source is increased to the given power level.

9. The image projection apparatus of claim 1 , further comprising at least one of a first detector to detect illuminance of the projection image projected on the projection face, and a second detector to detect luminance of the projection image output from the image projection apparatus, wherein the image luminance controller controls the light modulator based on at least one of a first detection result detected by the first detector and a second detection result detected by the second detector.

10. A method of controlling an image projection by an image projection apparatus comprising the steps of: emitting light from a light source; modulating intensity of the light emitted from the light source for generating a projection image; and controlling brightness of the projection image projected on a projection face at a substantially constant level during a given time period of the image projection apparatus, the given time period being from one time point when power supply to the image projection apparatus is started to another time point when a power level for driving the light source is increased to a given power level.

11. A non-transitory computer-readable storage medium storing a program that, when executed by a computer, causes the computer to execute a method of controlling an image projection by an image projection apparatus comprising the steps of: emitting light from a light source; modulating intensity of the light emitted from the light source for generating a projection image; and controlling brightness of the projection image projected on a projection face at a substantially constant level during a given time period of the image projection apparatus, the given time period being from one time point when power supply to the image projection apparatus is started to another time point when a power level for driving the light source is increased to a given power level.